All things being equal, you'd want the heavier rider as captain, but cycling skills can easily compensate as long as the stoker does not throw his/her weight around (which would be a problem in any case even with a light stoker).

So the answer really is what works for you, if you have the luxury to test it. Many of us don't have the option of switching with the stoker because the shorter rider often is too small for the captain's bike size.

Most people find that heavier at the front works better since it's like riding a bike with panniers (easy) versus trying to ride with a fridge sitting on the back of the bike (Not easy). Try it and you will soon see for yourself. (I mean swapping places, not riding with a fridge)

Only exception to the rule is where weight differences are not huge and lighter rider has better bike skills.

Whoever of your team is more comfortable/able to pilot the tandem takes the front.
Have piloted a tandem with a stoker twice my weight . . . no probs, 'til stoker tried steering from the back!
Agree that it must be nice that either one of you will fit front/rear of your twicer.